1. Technical Field
The present invention relates to a color filter ink, a color filter, an image display device, and an electronic device.
2. Related Art
Color filters are generally used in liquid crystal display devices (LCD) and the like that display color.
Color filters have conventionally been manufactured using a so-called photolithography method in which a coating film composed of a material (color layer formation composition) that includes a colorant, a photosensitive resin, a functional monomer, a polymerization initiator, and other components is formed on a substrate, and then photosensitive processing for radiating light via a photomask, development processing, and the like are performed. In such a method, the color filters are usually manufactured by repeating a process in which a coating film corresponding to each color is formed on substantially the entire surface of the substrate, only a portion of the coating film is cured, and most of the film other than the cured portion is removed, so that there is no color overlap. Therefore, only a portion of the coating film formed in color filter manufacturing remains as a color layer in the finished color filter, and most of the coating film is removed in the manufacturing process. Therefore, not only does the manufacturing cost of the color filter increase, but the process is also undesirable from the perspective of resource saving.
Methods have recently been proposed for forming the color layer of a color filter through the use of an inkjet head (droplet discharge head) (see Japanese Laid-Open Patent Application No. 2002-372613, for example). In such a method, because the discharge position and the like of droplets of the material (color layer formation composition) used to form the color layer are easily controlled, and waste of the color layer formation composition can be reduced, the environmental impact can be reduced, and manufacturing cost can also be minimized. However, in a method for manufacturing a color filter using an inkjet head, when droplets are discharged for long periods of time, and droplets are discharged continuously, the trajectory of the discharged droplets changes (so-called flight deflection occurs), it becomes impossible to land the droplets in the desired region, the droplet discharge quantity becomes unstable, and other problems occur. When such problems occur, on the substrate or the like onto which the droplets are to be discharged, the plurality of types of ink used to form different colored portions mixes together (colors mix), and the color saturation fluctuates between the plurality of colored portions that are originally supposed to have the same color saturation, and as a result, uneven color between regions of the same color filter, uneven saturation, and the like occur, fluctuation occurs in the characteristics (particularly contrast ratio, color reproduction range, and other color characteristics) between numerous color filters, and the reliability of the color filters is reduced. Since the droplet discharge device (industrial) used for color filter manufacturing is entirely different from what is used for a printer (consumer-level), and the droplet discharge device is used for mass production and droplet discharge onto large-scale workpieces (substrates), for example, there is a need to discharge large quantities of droplets for long periods of time. Because the droplet discharge device is used under such harsh conditions, the droplet discharge quantity easily fluctuates in comparison to a consumer droplet discharge device, but when the discharge quantity varies in this manner, fluctuation of the characteristics between numerous manufactured color filters, or fluctuation in the color saturation in different areas of a color filter occurs, and the reliability of the color filter as a product is markedly reduced.
Pigments generally have superior light fastness and other characteristics in comparison to dyes, and pigments are therefore widely used as colorants in color filter ink. However, when a pigment is used as the colorant, problems such as described above that accompany discharging the color filter ink from an inkjet head occur with greater severity. When a pigment is used as the colorant, severe drawbacks occur in that it is difficult to obtain adequately excellent contrast in the image displayed using the manufactured color filter, and when numerous color filters are manufactured by the inkjet method, the contrast characteristics of the manufactured color filters are severely compromised.